(MFC) Generate RSA Key and Sign a String

See more RSA Examples

Demonstrates how to generate a new RSA public/private key pair and use it to generate a signature for a string. The (binary) digital signature is returned as a hexidecimalized string.

Chilkat C/C++ Library Downloads MS Visual C/C++ Libs

See Also: Using MFC CString in Chilkat

#include <CkRsa.h>

void ChilkatSample(void)
    {
    CkString strOut;

    // This example assumes the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    CkRsa rsa;

    // Generate a 2048-bit RSA key.
    bool success = rsa.GenerateKey(2048);

    // To return the signature in hex.
    rsa.put_EncodingMode("hex");

    const char *strData = "This is the string to be signed.";

    // Sign the SHA256 hash of the string.
    const char *hexSig = rsa.signStringENC(strData,"sha256");

    strOut.append(hexSig);
    strOut.append("\r\n");
    strOut.append(rsa.lastErrorText());
    strOut.append("\r\n");

    // Now verify the signature:
    success = rsa.VerifyStringENC(strData,"sha256",hexSig);
    if (success == true) {
        strOut.append("Signature verified!");
        strOut.append("\r\n");
    }
    else {
        strOut.append(rsa.lastErrorText());
        strOut.append("\r\n");
    }

    // Try it with an invalid signature:
    success = rsa.VerifyStringENC(strData,"sha256","not a valid sig");
    if (success == true) {
        strOut.append("Signature verified!");
        strOut.append("\r\n");
    }
    else {
        strOut.append(rsa.lastErrorText());
        strOut.append("\r\n");
    }

    // Try it with invalid data:
    success = rsa.VerifyStringENC("Not the original data","sha256",hexSig);
    if (success == true) {
        strOut.append("Signature verified!");
        strOut.append("\r\n");
    }
    else {
        strOut.append(rsa.lastErrorText());
        strOut.append("\r\n");
    }

    // Try it with the wrong hash algorithm:
    success = rsa.VerifyStringENC(strData,"sha-1",hexSig);
    if (success == true) {
        strOut.append("Signature verified!");
        strOut.append("\r\n");
    }
    else {
        strOut.append(rsa.lastErrorText());
        strOut.append("\r\n");
    }



    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }